The present invention relates to an apparatus for operating the clamping jaws of a heavy-duty or power chuck that is part of a machining tool, with the clamping jaws being radially displaceably guided in a driven chuck body. The clamping jaws are coupled with a rotatable or axially displaceable adjustment member via wedge-type members, wedge hooks, levers, or similar intermediate means, and the adjustment member is in driving connection with an adjusting drive mechanism for producing an adjustment movement.
An apparatus of this general type is known from German Offenlegungsschrift No. 32 18 084-Bald dated Nov. 13, 1986. The adjusting drive mechanism of this known embodiment comprises an overlapping gear arrangement, the input member of which is supported on the main spindle of the machining tool, and the output member of which is connected with a movement-conversion system via which the alteration of the clamping force exerted upon a workpiece is effected; this known gear arrangement also comprises a variably embodied adjustment energy converter. To avoid large rotating masses, the adjustment energy converter is stationary and cooperates with an overlapping input provided between the input member and the output member of the gear arrangement, so that a torque can be produced between these two parts for an adjustment movement.
The adjustment energy converter can be in the form of an electromagnetic converter for producing alternating magnetic fields, or it can be embodied for the conversion of mechanical energy into the energy of alternating magnetic fields, with the operative connection to the transmission input of the overlapping gear arrangement being effected by a magnetic coupling. However, it is also possible to use an electric motor or a compressed air motor as the adjustment energy converter.
To reinforce the moment of reaction, the adjustment energy converters, the drive moment of which at the overlapping input of the gear arrangement is applied to the latter, should be arranged stationarily, which means that a considerable amount of space is absolutely necessary. Aside from the fact that the overlapping gear arrangement is similarly large, and is expensive to manufacture, it is very expensive to supply the power needed by the gear arrangement for producing an adjustment movement. If an electric motor or a compressed air motor is provided as the adjustment energy converter, it is necessary, in order to provide a driving connection with the overlapping gear arrangement, to connect at the output side of the converter a planetary gear system that continuously rotates at the speed of the main spindle of the machining tool. Aside from the fact that undesirable noises are caused by the continuously rotating planetary gear system, with this heretofore known apparatus not only is the capital expenditure extremely high for producing for an adjustment movement, so that the apparatus is expensive to manufacture, but, due to the large number of components that are required and that take part in the transfer of force, considerable power and efficiency losses have to be taken into consideration, and the susceptibility to breakdown is considerable.
It is therefore an object of the present invention to provide an apparatus of the aforementioned general type with which it is possible to operate the clamping jaws of a chuck at any time, even during operation of the spindle at high speeds, in an extremely reliable manner without having to directly engage the machining tool, and without requiring a particularly great capital expenditure. Rather, for this purpose, only a very small amount of space should be required in the region of the main spindle, and no or only slight thermal stresses and efficiency losses should occur due to friction. Furthermore, a clamping force should be easy to adjust and alter without difficulty, and should also be continuously maintained and should be capable of reproduction with no problems for the same conditions. However, above all, the inventive apparatus should be easy to handle, should be extremely reliable, and should have a long service life.